Bitrate of Download drops from 1,9Mbit to 219kbit

[Beastyboys]

I transfered a Game via FTP to my Vita with an average of 1,9Mbit.
The Games did so too.
Now the Bitrate dropped to ca. 220kbit and stays here. Sometimes grows up to 450kbit and stays at this Lvl.

Can you tell me where the Problem is?
My Internet Connection got 400.000Kbit Download- and 20.000kbit Upload Rate.
My Pc is connected via Lan and the Wlan goes trough my Settop Box.

greetings Beastyboys